MAITOTOXIN INDUCES THE ACROSOME REACTION IN MAMMALIAN SPERM OPENING A DIFFERENT CHANNEL THAN THE ZONA PELLUCIDA.

CHAVEZ JC; DE LA VEGA JL; DE BLAS GA; OCAMPO AY; CHIRINOS M; DARSZON A; TREVIÑO CL

Holderness School, Holderness, New Hampshire. USA.

Congreso; Gordon Research Conference: Fertilization & Activation Of Development; 2009

Gordon Research Conference

The acrosome reaction (AR) is an absolute requirement for sperm and egg fusion. Influx of Ca2+ into sperm cells through voltage dependent Ca2+ channels as well as store operated channels (SOC’s) have been implicated in this process. We have previously shown that MTx potently induces the AR in mouse sperm displaying a similar pharmacology to the ZP-induced AR. The lack of native human ZP has prevented a detailed study of the physiological cascade that leads to the AR in human sperm. In this work we used recombinant human ZP3 (rZP3) and two MTx channel blockers (U73122 and U73343) to further investigate and compare the MTX-and ZP3 induced AR in both species. We report here that MTx also induces the AR in human sperm, and as expected this induction is blocked by U73122 and U73343, however the rZP3 induction is only blocked by U73122 and not U73343 suggesting a distinct pathway. Since U73122 but not U73343 can block PLC, we used edelfosine (another PLC blocker) and observed that it also blocked the rZP3-induced AR, confirming that PLC is indeed involved in the human ZP3 signaling cascade. For comparison we performed the same set of experiments with mouse sperm, however, the MTx-induced mouse AR could not be fully characterized due to the fact that U73122 caused by itself a [Ca2+] increase in mouse sperm.